In this application we propose a study of the metabolism of the nonsteroidal antiestrogens 2-5, comounds presently of interest mainly for their potential use in cancer chemotherapy. Biochemical studies have suggested that the addition of a phenolic hydroxyl group to the structure of the antiestrogens greatly increases estrogen receptor binding, an event necessary for activity. Thus, attention will be focused on isolation and structural characterization of phenolic metabolites of these comounds, as produced in the presence of rat liver and intestinal microsomes, and in urine, feces, and blood plasma of rats after oral administration of these compounds. Results of this work should help define the potential of drug metabolizing enzymes for modulation of the pharmacological properties of 2-5.